/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.primitives;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static java.lang.Float.NEGATIVE_INFINITY;
import static java.lang.Float.POSITIVE_INFINITY;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Converter;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.CheckForNull;
import javax.annotation.Nullable;

/**
 * Static utility methods pertaining to {@code float} primitives, that are not already found in
 * either {@link Float} or {@link Arrays}.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@GwtCompatible(emulated = true)
public final class Floats {
    private Floats() {}

    /**
     * The number of bytes required to represent a primitive {@code float} value.
     *
     * <p>
     * <b>Java 8 users:</b> use {@link Float#BYTES} instead.
     *
     * @since 10.0
     */
    public static final int BYTES = Float.SIZE / Byte.SIZE;

    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Float) value).hashCode()}.
     *
     * <p>
     * <b>Java 8 users:</b> use {@link Float#hashCode(float)} instead.
     *
     * @param value a primitive {@code float} value
     * @return a hash code for the value
     */
    public static int hashCode(float value) {
        // TODO(kevinb): is there a better way, that's still gwt-safe?
        return ((Float) value).hashCode();
    }

    /**
     * Compares the two specified {@code float} values using {@link Float#compare(float, float)}.
     * You may prefer to invoke that method directly; this method exists only for consistency with
     * the other utilities in this package.
     *
     * <p>
     * <b>Note:</b> this method simply delegates to the JDK method {@link Float#compare}. It is
     * provided for consistency with the other primitive types, whose compare methods were not added
     * to the JDK until JDK 7.
     *
     * @param a the first {@code float} to compare
     * @param b the second {@code float} to compare
     * @return the result of invoking {@link Float#compare(float, float)}
     */
    public static int compare(float a, float b) {
        return Float.compare(a, b);
    }

    /**
     * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but
     * not necessarily implemented as, {@code !(Float.isInfinite(value) || Float.isNaN(value))}.
     *
     * <p>
     * <b>Java 8 users:</b> use {@link Float#isFinite(float)} instead.
     *
     * @since 10.0
     */
    public static boolean isFinite(float value) {
        return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
    }

    /**
     * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
     * Note that this always returns {@code false} when {@code
     * target} is {@code NaN}.
     *
     * @param array an array of {@code float} values, possibly empty
     * @param target a primitive {@code float} value
     * @return {@code true} if {@code array[i] == target} for some value of {@code
     *     i}
     */
    public static boolean contains(float[] array, float target) {
        for (float value : array) {
            if (value == target) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns the index of the first appearance of the value {@code target} in {@code array}. Note
     * that this always returns {@code -1} when {@code target} is {@code NaN}.
     *
     * @param array an array of {@code float} values, possibly empty
     * @param target a primitive {@code float} value
     * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
     *         such index exists.
     */
    public static int indexOf(float[] array, float target) {
        return indexOf(array, target, 0, array.length);
    }

    // TODO(kevinb): consider making this public
    private static int indexOf(float[] array, float target, int start, int end) {
        for (int i = start; i < end; i++) {
            if (array[i] == target) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the start position of the first occurrence of the specified {@code
     * target} within {@code array}, or {@code -1} if there is no such occurrence.
     *
     * <p>
     * More formally, returns the lowest index {@code i} such that
     * {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as
     * {@code target}.
     *
     * <p>
     * Note that this always returns {@code -1} when {@code target} contains {@code NaN}.
     *
     * @param array the array to search for the sequence {@code target}
     * @param target the array to search for as a sub-sequence of {@code array}
     */
    public static int indexOf(float[] array, float[] target) {
        checkNotNull(array, "array");
        checkNotNull(target, "target");
        if (target.length == 0) {
            return 0;
        }

        outer: for (int i = 0; i < array.length - target.length + 1; i++) {
            for (int j = 0; j < target.length; j++) {
                if (array[i + j] != target[j]) {
                    continue outer;
                }
            }
            return i;
        }
        return -1;
    }

    /**
     * Returns the index of the last appearance of the value {@code target} in {@code array}. Note
     * that this always returns {@code -1} when {@code target} is {@code NaN}.
     *
     * @param array an array of {@code float} values, possibly empty
     * @param target a primitive {@code float} value
     * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if
     *         no such index exists.
     */
    public static int lastIndexOf(float[] array, float target) {
        return lastIndexOf(array, target, 0, array.length);
    }

    // TODO(kevinb): consider making this public
    private static int lastIndexOf(float[] array, float target, int start, int end) {
        for (int i = end - 1; i >= start; i--) {
            if (array[i] == target) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the least value present in {@code array}, using the same rules of comparison as
     * {@link Math#min(float, float)}.
     *
     * @param array a <i>nonempty</i> array of {@code float} values
     * @return the value present in {@code array} that is less than or equal to every other value in
     *         the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    public static float min(float... array) {
        checkArgument(array.length > 0);
        float min = array[0];
        for (int i = 1; i < array.length; i++) {
            min = Math.min(min, array[i]);
        }
        return min;
    }

    /**
     * Returns the greatest value present in {@code array}, using the same rules of comparison as
     * {@link Math#max(float, float)}.
     *
     * @param array a <i>nonempty</i> array of {@code float} values
     * @return the value present in {@code array} that is greater than or equal to every other value
     *         in the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    public static float max(float... array) {
        checkArgument(array.length > 0);
        float max = array[0];
        for (int i = 1; i < array.length; i++) {
            max = Math.max(max, array[i]);
        }
        return max;
    }

    /**
     * Returns the value nearest to {@code value} which is within the closed range
     * {@code [min..max]}.
     *
     * <p>
     * If {@code value} is within the range {@code [min..max]}, {@code value} is returned unchanged.
     * If {@code value} is less than {@code min}, {@code min} is returned, and if {@code value} is
     * greater than {@code max}, {@code max} is returned.
     *
     * @param value the {@code float} value to constrain
     * @param min the lower bound (inclusive) of the range to constrain {@code value} to
     * @param max the upper bound (inclusive) of the range to constrain {@code value} to
     * @throws IllegalArgumentException if {@code min > max}
     * @since 21.0
     */
    @Beta
    public static float constrainToRange(float value, float min, float max) {
        checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
        return Math.min(Math.max(value, min), max);
    }

    /**
     * Returns the values from each provided array combined into a single array. For example,
     * {@code concat(new float[] {a, b}, new float[] {}, new float[] {c}} returns the array
     * {@code {a, b, c}}.
     *
     * @param arrays zero or more {@code float} arrays
     * @return a single array containing all the values from the source arrays, in order
     */
    public static float[] concat(float[]... arrays) {
        int length = 0;
        for (float[] array : arrays) {
            length += array.length;
        }
        float[] result = new float[length];
        int pos = 0;
        for (float[] array : arrays) {
            System.arraycopy(array, 0, result, pos, array.length);
            pos += array.length;
        }
        return result;
    }

    private static final class FloatConverter extends Converter<String, Float> implements Serializable {
        static final FloatConverter INSTANCE = new FloatConverter();

        @Override
        protected Float doForward(String value) {
            return Float.valueOf(value);
        }

        @Override
        protected String doBackward(Float value) {
            return value.toString();
        }

        @Override
        public String toString() {
            return "Floats.stringConverter()";
        }

        private Object readResolve() {
            return INSTANCE;
        }

        private static final long serialVersionUID = 1;
    }

    /**
     * Returns a serializable converter object that converts between strings and floats using
     * {@link Float#valueOf} and {@link Float#toString()}.
     *
     * @since 16.0
     */
    @Beta
    public static Converter<String, Float> stringConverter() {
        return FloatConverter.INSTANCE;
    }

    /**
     * Returns an array containing the same values as {@code array}, but guaranteed to be of a
     * specified minimum length. If {@code array} already has a length of at least
     * {@code minLength}, it is returned directly. Otherwise, a new array of size
     * {@code minLength + padding} is returned, containing the values of {@code array}, and zeroes
     * in the remaining places.
     *
     * @param array the source array
     * @param minLength the minimum length the returned array must guarantee
     * @param padding an extra amount to "grow" the array by if growth is necessary
     * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
     * @return an array containing the values of {@code array}, with guaranteed minimum length
     *         {@code minLength}
     */
    public static float[] ensureCapacity(float[] array, int minLength, int padding) {
        checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
        checkArgument(padding >= 0, "Invalid padding: %s", padding);
        return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
    }

    /**
     * Returns a string containing the supplied {@code float} values, converted to strings as
     * specified by {@link Float#toString(float)}, and separated by {@code separator}. For example,
     * {@code join("-", 1.0f, 2.0f, 3.0f)} returns the string {@code "1.0-2.0-3.0"}.
     *
     * <p>
     * Note that {@link Float#toString(float)} formats {@code float} differently in GWT. In the
     * previous example, it returns the string {@code
     * "1-2-3"}.
     *
     * @param separator the text that should appear between consecutive values in the resulting
     *        string (but not at the start or end)
     * @param array an array of {@code float} values, possibly empty
     */
    public static String join(String separator, float... array) {
        checkNotNull(separator);
        if (array.length == 0) {
            return "";
        }

        // For pre-sizing a builder, just get the right order of magnitude
        StringBuilder builder = new StringBuilder(array.length * 12);
        builder.append(array[0]);
        for (int i = 1; i < array.length; i++) {
            builder.append(separator).append(array[i]);
        }
        return builder.toString();
    }

    /**
     * Returns a comparator that compares two {@code float} arrays
     * <a href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is,
     * it compares, using {@link #compare(float, float)}), the first pair of values that follow any
     * common prefix, or when one array is a prefix of the other, treats the shorter array as the
     * lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f] < [2.0f]}.
     *
     * <p>
     * The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
     * support only identity equality), but it is consistent with
     * {@link Arrays#equals(float[], float[])}.
     *
     * @since 2.0
     */
    public static Comparator<float[]> lexicographicalComparator() {
        return LexicographicalComparator.INSTANCE;
    }

    private enum LexicographicalComparator implements Comparator<float[]> {
        INSTANCE;

        @Override
        public int compare(float[] left, float[] right) {
            int minLength = Math.min(left.length, right.length);
            for (int i = 0; i < minLength; i++) {
                int result = Float.compare(left[i], right[i]);
                if (result != 0) {
                    return result;
                }
            }
            return left.length - right.length;
        }

        @Override
        public String toString() {
            return "Floats.lexicographicalComparator()";
        }
    }

    /**
     * Returns an array containing each value of {@code collection}, converted to a {@code float}
     * value in the manner of {@link Number#floatValue}.
     *
     * <p>
     * Elements are copied from the argument collection as if by {@code
     * collection.toArray()}. Calling this method is as thread-safe as calling that method.
     *
     * @param collection a collection of {@code Number} instances
     * @return an array containing the same values as {@code collection}, in the same order,
     *         converted to primitives
     * @throws NullPointerException if {@code collection} or any of its elements is null
     * @since 1.0 (parameter was {@code Collection<Float>} before 12.0)
     */
    public static float[] toArray(Collection<? extends Number> collection) {
        if (collection instanceof FloatArrayAsList) {
            return ((FloatArrayAsList) collection).toFloatArray();
        }

        Object[] boxedArray = collection.toArray();
        int len = boxedArray.length;
        float[] array = new float[len];
        for (int i = 0; i < len; i++) {
            // checkNotNull for GWT (do not optimize)
            array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue();
        }
        return array;
    }

    /**
     * Returns a fixed-size list backed by the specified array, similar to
     * {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any
     * attempt to set a value to {@code null} will result in a {@link NullPointerException}.
     *
     * <p>
     * The returned list maintains the values, but not the identities, of {@code Float} objects
     * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true
     * for the returned list is unspecified.
     *
     * <p>
     * The returned list may have unexpected behavior if it contains {@code
     * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
     *
     * @param backingArray the array to back the list
     * @return a list view of the array
     */
    public static List<Float> asList(float... backingArray) {
        if (backingArray.length == 0) {
            return Collections.emptyList();
        }
        return new FloatArrayAsList(backingArray);
    }

    @GwtCompatible
    private static class FloatArrayAsList extends AbstractList<Float> implements RandomAccess, Serializable {
        final float[] array;
        final int start;
        final int end;

        FloatArrayAsList(float[] array) {
            this(array, 0, array.length);
        }

        FloatArrayAsList(float[] array, int start, int end) {
            this.array = array;
            this.start = start;
            this.end = end;
        }

        @Override
        public int size() {
            return end - start;
        }

        @Override
        public boolean isEmpty() {
            return false;
        }

        @Override
        public Float get(int index) {
            checkElementIndex(index, size());
            return array[start + index];
        }

        @Override
        public boolean contains(Object target) {
            // Overridden to prevent a ton of boxing
            return (target instanceof Float) && Floats.indexOf(array, (Float) target, start, end) != -1;
        }

        @Override
        public int indexOf(Object target) {
            // Overridden to prevent a ton of boxing
            if (target instanceof Float) {
                int i = Floats.indexOf(array, (Float) target, start, end);
                if (i >= 0) {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public int lastIndexOf(Object target) {
            // Overridden to prevent a ton of boxing
            if (target instanceof Float) {
                int i = Floats.lastIndexOf(array, (Float) target, start, end);
                if (i >= 0) {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public Float set(int index, Float element) {
            checkElementIndex(index, size());
            float oldValue = array[start + index];
            // checkNotNull for GWT (do not optimize)
            array[start + index] = checkNotNull(element);
            return oldValue;
        }

        @Override
        public List<Float> subList(int fromIndex, int toIndex) {
            int size = size();
            checkPositionIndexes(fromIndex, toIndex, size);
            if (fromIndex == toIndex) {
                return Collections.emptyList();
            }
            return new FloatArrayAsList(array, start + fromIndex, start + toIndex);
        }

        @Override
        public boolean equals(@Nullable Object object) {
            if (object == this) {
                return true;
            }
            if (object instanceof FloatArrayAsList) {
                FloatArrayAsList that = (FloatArrayAsList) object;
                int size = size();
                if (that.size() != size) {
                    return false;
                }
                for (int i = 0; i < size; i++) {
                    if (array[start + i] != that.array[that.start + i]) {
                        return false;
                    }
                }
                return true;
            }
            return super.equals(object);
        }

        @Override
        public int hashCode() {
            int result = 1;
            for (int i = start; i < end; i++) {
                result = 31 * result + Floats.hashCode(array[i]);
            }
            return result;
        }

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder(size() * 12);
            builder.append('[').append(array[start]);
            for (int i = start + 1; i < end; i++) {
                builder.append(", ").append(array[i]);
            }
            return builder.append(']').toString();
        }

        float[] toFloatArray() {
            return Arrays.copyOfRange(array, start, end);
        }

        private static final long serialVersionUID = 0;
    }

    /**
     * Parses the specified string as a single-precision floating point value. The ASCII character
     * {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
     *
     * <p>
     * Unlike {@link Float#parseFloat(String)}, this method returns {@code null} instead of throwing
     * an exception if parsing fails. Valid inputs are exactly those accepted by
     * {@link Float#valueOf(String)}, except that leading and trailing whitespace is not permitted.
     *
     * <p>
     * This implementation is likely to be faster than {@code
     * Float.parseFloat} if many failures are expected.
     *
     * @param string the string representation of a {@code float} value
     * @return the floating point value represented by {@code string}, or {@code null} if
     *         {@code string} has a length of zero or cannot be parsed as a {@code float} value
     * @since 14.0
     */
    @Beta
    @Nullable
    @CheckForNull
    @GwtIncompatible // regular expressions
    public static Float tryParse(String string) {
        if (Doubles.FLOATING_POINT_PATTERN.matcher(string).matches()) {
            // TODO(lowasser): could be potentially optimized, but only with
            // extensive testing
            try {
                return Float.parseFloat(string);
            } catch (NumberFormatException e) {
                // Float.parseFloat has changed specs several times, so fall through
                // gracefully
            }
        }
        return null;
    }
}
